Tatsuo Adachi

The University of Tokyo, Edo, Tōkyō, Japan

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Publications (8)41.72 Total impact

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    ABSTRACT: To obtain therapeutically effective new antibiotics, we first searched for bacterial culture supernatants with antimicrobial activity in vitro and then performed a secondary screening using the silkworm infection model. Through further purification of the in vivo activity, we obtained a compound with a previously uncharacterized structure and named it 'lysocin E'. Lysocin E interacted with menaquinone in the bacterial membrane to achieve its potent bactericidal activity, a mode of action distinct from that of any other known antibiotic, indicating that lysocin E comprises a new class of antibiotic. This is to our knowledge the first report of a direct interaction between a small chemical compound and menaquinone that leads to bacterial killing. Furthermore, lysocin E decreased the mortality of infected mice. To our knowledge, lysocin E is the first compound identified and purified by quantitative measurement of therapeutic effects in an invertebrate infection model that exhibits robust in vivo effects in mammals.
    Nature Chemical Biology 12/2014; · 12.95 Impact Factor
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    ABSTRACT: Injection of culture supernatant of Serratia marcescens, a Gram-negative bacterium pathogenic to a wide range of host animals including insects and mammals, into the hemolymph of silkworm (Bombyx mori) larvae led to continuous flow of the hemolymph (blood of insects) from the injection site. The amount of hemolymph lost within 60 min reached 15% to 20% of the total larval weight. Using a bioassay with live silkworms, we purified Serralysin, a metalloprotease that requires divalent cations for its activity, as the factor responsible for the promotion of hemolymph bleeding from the culture supernatant of S. marcescens. Recombinant protein also induced hemolymph bleeding in silkworms. Moreover, the culture supernatant of an S. marcescens disruption mutant of the ser gene showed attenuated ability to promote hemolymph bleeding. In addition, this bleeding-promoting activity of the S. marcescens culture supernatant was attenuated by disruption of the wecA gene, which is involved in the biosynthesis of the lipopolysaccharide O-antigen. These findings suggest that Serralysin metalloprotease contributes to the pathogenesis of S. marcescens by inhibiting wound healing, which leads to a massive loss of hemolymph from silkworm larvae.
    Journal of Invertebrate Pathology 03/2014; · 2.67 Impact Factor
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    ABSTRACT: We performed a genome-wide analysis using a next-generation sequencer to investigate the effect of pulmonary surfactant on gene expression in Staphylococcus aureus, a clinically important opportunistic pathogen. RNA-seq analysis of bacterial transcripts at late log-phase revealed 142 genes that were upregulated by more than 2-fold following the addition of pulmonary surfactant to the culture medium. Among these genes, we confirmed by quantitative reverse transcription-polymerase chain reaction analysis that mRNA amounts of genes encoding ESAT-6 secretion system C (EssC); an unknown hypothetical protein, NWMN_0246 (pulmonary surfactant-inducible factor A; PsiA); and hemolysin gamma subunit B (HlgB) were increased 3 to 10-fold by the surfactant treatment. Among the major constituents of pulmonary surfactant, phospholipids and palmitate, only palmitate, which is the most abundant fatty acid in the pulmonary surfactant and a known antibacterial substance, stimulated the expression of these three genes. Moreover, these genes were also induced by supplementing the culture with detergents. The induction of gene expression by surfactant or palmitate was not observed in a disruption mutant of the sigB gene that encodes an alternative sigma factor involved in bacterial stress responses. Furthermore, each disruption mutant of the essC, psiA, or hlgB gene showed attenuation of both survival in the lung and host killing ability in a murine pneumonia model. These findings suggest that S. aureus resists membrane stress caused by free fatty acids present in the pulmonary surfactant through the regulation of virulence gene expression, which contributes to its pathogenesis within the lungs of the host animal.
    Infection and immunity 01/2014; · 4.21 Impact Factor
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    ABSTRACT: Silkworm hemolymph induced both the cessation of growth and an increase in triglyceride storage in BmN4 cells. We purified the growth inhibitory factor from the silkworm hemolymph and identified this protein as the Bombyx mori Promoting Protein, an ortholog of Niemann-Pick disease type C2 (NPC2) protein. Recombinant silkworm NPC2 inhibited cellular proliferation and increased triglyceride accumulation in BmN4 cells. Injection of either the recombinant protein or antiserum of NPC2 into living silkworms increased or decreased, respectively, triglyceride levels in the fat body. A mutation that depletes the cholesterol-binding capacity did not abolish the activity of NPC2. We further revealed that NPC2 induced the phosphorylation of AMP-activated protein kinase (AMPK) and that an AMPK inhibitor suppressed NPC2-dependent triglyceride accumulation. These findings suggest that NPC2 induces triglyceride accumulation via the activation of AMPK independently of its cholesterol-binding capacity in the silkworm.
    Biochemical Journal 01/2014; · 4.65 Impact Factor
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    ABSTRACT: Injection of a culture supernatant of Serratia marcescens into the bloodstream of the silkworm Bombyx mori increased the number of freely circulating immunosurveillance cells (hemocytes). Using a bioassay with live silkworms, serralysin metalloprotease was purified from the culture supernatant and identified as the factor responsible for this activity. Serralysin inhibited the in vitro attachment of both silkworm hemocytes and murine peritoneal macrophages. Incubation of silkworm hemocytes or murine macrophages with serralysin resulted in degradation of the cellular immune factor BmSPH-1 or calreticulin, respectively. Furthermore, serralysin suppressed in vitro phagocytosis of bacteria by hemocytes and in vivo bacterial clearance in silkworms. Disruption of the serralysin gene in S. marcescens attenuated its host killing ability in silkworms and mice. These findings suggest that serralysin metalloprotease secreted by S. marcescens suppresses cellular immunity by decreasing the adhesive properties of immunosurveillance cells, thereby contributing to bacterial pathogenesis.
    Journal of Biological Chemistry 01/2014; · 4.65 Impact Factor
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    ABSTRACT: Insect cytokine paralytic peptide (PP) upregulates the expression of immune-related genes and contributes to host defense in the silkworm Bombyx mori. The present findings demonstrated that PP promotes nitric oxide (NO) production and induces the expression of NO synthase. A pharmacologic NO synthase inhibitor suppressed the PP-dependent i) induction of immune-related genes, ii) activation of p38 mitogen-activated protein kinase, and iii) killing delay of silkworm larvae by Staphylococcus aureus. The upstream mechanism of NO synthesis in insect immunity has been unknown, and the present results suggest for the first time that an insect cytokine induces NO and contributes to self-defense.
    Developmental and comparative immunology 11/2012; · 3.29 Impact Factor
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    ABSTRACT: Injection of Serratia marcescens into the blood (hemolymph) of the silkworm, Bombyx mori, induced the activation of c-Jun NH(2)-terminal kinase (JNK), followed by caspase activation and apoptosis of blood cells (hemocytes). This process impaired the innate immune response in which pathogen cell wall components, such as glucan, stimulate hemocytes, leading to the activation of insect cytokine paralytic peptide. S. marcescens induced apoptotic cell death of silkworm hemocytes and mouse peritoneal macrophages in vitro. We searched for S. marcescens transposon mutants with attenuated ability to induce apoptosis of silkworm hemocytes. Among the genes identified, disruption mutants of wecA (a gene involved in lipopolysaccharide O-antigen synthesis), and flhD and fliR (essential genes in flagella synthesis) showed reduced motility and impaired induction of mouse macrophage cell death. These findings suggest that S. marcescens induces apoptosis of host immune cells via lipopolysaccharide- and flagella-dependent motility, leading to the suppression of host innate immunity.
    Journal of Biological Chemistry 08/2012; 287(43):36582-92. · 4.65 Impact Factor
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    ABSTRACT: Porphyromonas gingivalis, a pathogen that causes inflammation in human periodontal tissue, killed silkworm (Bombyx mori, Lepidoptera) larvae when injected into the blood (hemolymph). Silkworm lethality was not rescued by antibiotic treatment, and heat-killed bacteria were also lethal. Heat-killed bacteria of mutant P. gingivalis strains lacking virulence factors also killed silkworms. Silkworms died after injection of peptidoglycans purified from P. gingivalis (pPG), and pPG toxicity was blocked by treatment with mutanolysin, a peptidoglycan-degrading enzyme. pPG induced silkworm hemolymph melanization at the same dose as that required to kill the animal. pPG injection increased caspase activity in silkworm tissues. pPG-induced silkworm death was delayed by injecting melanization-inhibiting reagents (a serine protease inhibitor and 1-phenyl-2-thiourea), antioxidants (N-acetyl-l-cysteine, glutathione, and catalase), and a caspase inhibitor (Ac-DEVD-CHO). Thus, pPG induces excessive activation of the innate immune response, which leads to the generation of reactive oxygen species and apoptotic cell death in the host tissue.
    Journal of Biological Chemistry 10/2010; 285(43):33338-47. · 4.65 Impact Factor

Publication Stats

25 Citations
41.72 Total Impact Points

Institutions

  • 2010–2014
    • The University of Tokyo
      • • Department of Pharmaceutical Sciences
      • • Faculty and Graduate School of Pharmaceutical Sciences
      Edo, Tōkyō, Japan